It has become an almost universal practice for cities and other similar bodies to provide a network of water lines and hydrants for fire fighting purposes, and it is typical for each hydrant location to be provided with a single main valve to open and close the water supply to each such hydrant, without providing a shut-off valve or valves to isolate each hydrant from the main water supply. After a period of time in service it is common for the main hydrant valves to develop leaks and other mechanical problems which require repair or replacement of the valve and valve seat located in the base of the hydrant. As a result of the lack of shut-off valves in the water lines running to and from each hydrant, it is necessary to either shut off the water supply to the entire network which includes the hydrant to be repaired or to perform the repair under full water pressure. Because shutting off the water supply both causes major inconvenience to local residents and renders the local fire protection system inoperative, it is desireable that the hydrant repair be performed under water pressure.
A typical fire hydrant generally comprises a base section which includes the hydrant valve and valve seat as well as the incoming and outgoing water service lines, an elongate barrel extending upward from the base section, and a bonnet which closes the upper end of the barrel and includes means of activating the hydrant valve. When the hydrant valve is opened, water is allowed to flow into the barrel of the hydrant under full pressure, and normally is allowed to flow from the barrel through hose fittings.
Various attempts to device an apparatus and method of removing and replacing hydrant valves without shutting off the water supply to the hydrant have been made, but such attempts have been only marginally successful. One approach to the problem is illustrated by U.S. Pat. No. 1,349,062, to Goldberg, which provides an apparatus intended to allow the main hydrant valve to be removed from the hydrant base and then isolated from the pressurized zone of the hydrant for replacement. The prior approaches provide a partial solution to the problem, but substantial difficulties have remained unresolved. Such difficulties include the problems of damage to the water supply lines during removal of the main hydrant valve, damage to the valve activating means during removal, blowout of the main hydrant valve upon its release from the hydrant base, water hammer during replacement of the valve, and damage to the valve and valve seat during replacement of the valve. These unresolved difficulties and disadvantages often result in damage to the water lines and hydrant base or damage to the replacement valve during the repair attempt to an extent which renders the repair ineffective or creates a situation which is worse than the original problem.
Accordingly, there has continued to be a need for a fully effective apparatus and method of removing and replacing the main hydrant valves without shutting off the water supply to the hydrant and without introducing the noted difficulties and disadvantages to the removal and replacement operation. It is an object of the present invention to provide an apparatus and method for repairing such hydrants in a manner which avoids stress and damage to the water supply lines and hydrant base, as well as avoiding damage to the replacement valve, valve seat and valve activating means. It is a further object of the present invention to provide an apparatus and method for repairing water hydrants in a highly efficient and rapid manner for the purpose of reducing both cost of repair and the time in which the hydrant is out of service.